From: Andreea-Cristina Bernat Date: Fri, 16 Jan 2015 15:19:53 +0000 (-0500) Subject: IB/qib: Replace rcu_assign_pointer() with RCU_INIT_POINTER() in qib_qp.c X-Git-Tag: firefly_0821_release~176^2~2252^2^8~4 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=03c885913f914d17124432dd50caf2923a80847c;p=firefly-linux-kernel-4.4.55.git IB/qib: Replace rcu_assign_pointer() with RCU_INIT_POINTER() in qib_qp.c According to RCU_INIT_POINTER()'s block comment 3.a, it can be used if "1. This use of RCU_INIT_POINTER() is NULLing out the pointer" it is better to use it instead of rcu_assign_pointer() because it has a smaller overhead. "3. The referenced data structure has already been exposed to readers either at compile time or via rcu_assign_pointer() -and- a. You have not made -any- reader-visible changes to this structure since then". These cases fulfill the conditions above because between the rcu_dereference_protected() call and the rcu_assign_pointer() call there is no update of that value. Therefore, this patch makes the replacement. The following Coccinelle semantic patch was used: @@ @@ - rcu_assign_pointer + RCU_INIT_POINTER (..., ( rtnl_dereference(...) | rcu_dereference_protected(...) ) ) [consolidated from http://marc.info/?l=linux-rdma&m=140836578119485&w=2 and http://marc.info/?l=linux-rdma&m=140906361403047&w=2] Tested-by: Mike Marciniszyn Signed-off-by: Andreea-Cristina Bernat Signed-off-by: Mike Marciniszyn Signed-off-by: Roland Dreier --- diff --git a/drivers/infiniband/hw/qib/qib_qp.c b/drivers/infiniband/hw/qib/qib_qp.c index 6ddc0264aad2..4fa88ba2963e 100644 --- a/drivers/infiniband/hw/qib/qib_qp.c +++ b/drivers/infiniband/hw/qib/qib_qp.c @@ -255,10 +255,10 @@ static void remove_qp(struct qib_ibdev *dev, struct qib_qp *qp) if (rcu_dereference_protected(ibp->qp0, lockdep_is_held(&dev->qpt_lock)) == qp) { - rcu_assign_pointer(ibp->qp0, NULL); + RCU_INIT_POINTER(ibp->qp0, NULL); } else if (rcu_dereference_protected(ibp->qp1, lockdep_is_held(&dev->qpt_lock)) == qp) { - rcu_assign_pointer(ibp->qp1, NULL); + RCU_INIT_POINTER(ibp->qp1, NULL); } else { struct qib_qp *q; struct qib_qp __rcu **qpp; @@ -269,7 +269,7 @@ static void remove_qp(struct qib_ibdev *dev, struct qib_qp *qp) lockdep_is_held(&dev->qpt_lock))) != NULL; qpp = &q->next) if (q == qp) { - rcu_assign_pointer(*qpp, + RCU_INIT_POINTER(*qpp, rcu_dereference_protected(qp->next, lockdep_is_held(&dev->qpt_lock))); removed = 1; @@ -315,7 +315,7 @@ unsigned qib_free_all_qps(struct qib_devdata *dd) for (n = 0; n < dev->qp_table_size; n++) { qp = rcu_dereference_protected(dev->qp_table[n], lockdep_is_held(&dev->qpt_lock)); - rcu_assign_pointer(dev->qp_table[n], NULL); + RCU_INIT_POINTER(dev->qp_table[n], NULL); for (; qp; qp = rcu_dereference_protected(qp->next, lockdep_is_held(&dev->qpt_lock)))